The present invention relates to members or elements for delivery of writing ink, e.g., fountain pen tips, thin rods or needles inserted in small diameter tube tips of small diameter tube writing instruments, ball point pen tips, balls of ball point pens and ball seats of ball point pens, and also to ink guides subject to wear caused by the writing surface either directly or indirectly via balls or the like.
Heretofore, various materials such as ceramics, metals and synthetic resins have been used as the materials of ink guide and suitably selected according to desired characters such as wear resistance, ink delivery property and touch of writing. Usually, inorganic materials such as ceramics and metals are used when there is a particular demand for the wear resistance, while organic materials such as synthetic resins are used when the touch of writing is taken into particular consideration. In other words, these materials are superior in some aspects but inferior in other aspects. Among the three different kinds of materials noted above, synthetic resins are used as the material of ink guide to which the invention appertains. Among such synthetic resins, those which are comparatively superior in wear resistance are selected, although the wear resistance is inferior compared to the other two kinds of materials noted above. More specifically, a large number of different synthetic resins are used for commercially available synthetic resin ink guides. A major proportion of these materials are made of polyacetals and polyamides.
Either polyacetals and polyamides however, do not have satisfactory wear resistance, although the wear resistance is superior among other synthetic resins. Therefore, a great change in the width of trace often results between the start and end of use. Or pen tip feed mechanisms are provided as additional structures to ensure long life of the writing tools.
The improvement of the wear resistance is thus greatly desired. Along with the wear resistance there are other properties which also have to be made satisfactory. One of such properties is the anti-clogging property. Even excellent wear resistance materials can not guarantee perfect freedom from wear. Therefore, the way in which the wears occurs is very important. If wear proceeds without being accompanied by sufficient division of molecules or very small particles, the material becomes frayed or nappy, resulting in an insufficient delivery of ink. In the ink guide, the ink delivery property is as important as the wear resistance. Also, if the anti-clogging property is deteriorated to a greater extent than the extent of improvement of the wear resistance, extension of life can not be promised.